In France some high speed trains go now directly to airports (CDG,LYO). So it is becoming possible to chain a plane and a train in a few scenarios.
For freight[1]. Putative high speed rail might go to the same places but generally can't share the same tracks with 30mph long haul trains. And the big gap is the plumbing of rail and transit into the urban cores, which in most US cities is highly decayed and in many of the newer metropolises was never built at all.
[1] Which is unsurprising, because we have the biggest per-capita need for transcontinental land freight transport in the world. The US has been perfectly fine at building out infrastructure it thinks it needs, it's just been making poor choices about what it "needs".
The evisceration of the passenger rail market was in large part caused by intentional urban planning. White flight moved a lot of people from city centers to suburbans where nary a black person could be found, and urban planners in turn abetted the process by building freeways straight through urban cores and turning every other city block into a parking lot in all but the very largest cities (well, except for LA). Uncoincidentally, the cities that didn't get turned into massive parking lots retained much more functional commuter rail systems than those cities that did.
E.g. Utah has a population density of 14km^2, similar to Norway. But like Norway, Utah has most of its population in a small portion of the area - the Salt Lake City–Provo–Orem Combined Statistical Area makes up 82% of the population.
Nebraska has a density of 9.63km^2, but Omaha-Council Bluffs + Lincoln makes up more than half the population (and that's ignoring the Iowa side of Omaha-Council Bluffs)
There are plenty of metropolitan areas like this in the US that may not have the density to justify much of an expansion to rail between them, but that are dense enough that a more rail oriented infrastructure within them would be possible.
And as you point out, this is with current US urban planning. If an expansion of rail is combined with adjustments to urban planning to encourage construction aligned with expanding transport systems, it'd become even more viable (e.g. near automatic planning permission for higher density near stations would probably in itself do a lot)
That play a role in usability. It’s a good environment to work, for instance.
... The trains departing from there are mostly low-cost trains rather than trains meant to be connecting with flights, and people taking them have to move to CDG instead of a better location.
It seems to be a service aimed at salvaging the infrastructure rather than an actual useful service.